This is the smallest dog sweater pattern I could find, I hope it helps you.

SIZE: width across shoulder, 8" length of back, 14"

MATERIALS; bucilla Win-Knit 4 ozs. and Melody 2 ozs., your color choice. ( I made one for a mini poodle and just used 4 ply yarn - all one color - and it turned out fine)
Knitting needles No. 7, or size required to fit gauge .
Gauge: 4sts and 6 rows = 1" stockinette st worked with one strand of each yarn held together

Next 7 rows: Repeat rows 2 and 1 alternately, continue to work in this manner working cable twists every 8th Row until 4" from beg.

Next Row: Inc 1 st after first marker and before last marker keeping 4 sts at each end in garter st and inc sts in stockinette st (k on right side, p on wrong side) and the remainder of sts in pat, repeat inc Row every other Row 8 times more - 50 sts on needle, work even until 10'
from beg, end wrong side.

Shape armholes: K4, dec 1 st, work to last 6 sts, dec 1 st, k4.

Next Row: work even

Repeat last 2 rows 8 times more - 32 sts on needle

Work until 14" from beg, end wrong side, Place sts on holder.

Front: cast on 23 sts. work in k1, p1, ribbing for 8" cast on 3 sts at end of next 2 rows.

Join sts on back and continue in ribbing across all sts for 3" for collar.

Bind off in ribbing

Finishing: sew back and front tog from last inc up to first dec.
Sew collar seam at right side, then turn collar over. Press lightly